Operating Instructions

Chapter 4 - Parameters and Menu Structure
I/O and Hardware (M5)
125 | 187
Siemens Industry, Inc.
Siemens BT300 HVAC Drive
DPD01809
Smart Infrastructure
2019-05-29
Table 87: Common Settings.
Structure
Parameter
Min.
Max.
Default
ID
Description
P5.8.1.1
Protocol
No Protocol
Modbus RTU
No Protocol
2208
Defines the RS-485 base fieldbus protocol to
be used:
0 = No Protocol
1 = N2
2 = BACnet MS/TP
3 = P14 = Modbus RTU
NOTE: A new menu will be accessible at
M5.8.3 depending upon the protocol selected.
Configuration for protocol communications
will be within that menu.
NOTE: This selection enables monitoring
only. If control (start/stop and speed
reference) is to be from fieldbus, then Ctrl.
Place Auto (P3.3.1) must be set to
FieldbusCTRL.
N2 (M5.8.3)
The N2 communications protocol is used by Johnson Controls and others to connect terminal unit controllers
to supervisory controllers. It is open to any manufacturer and based upon a simple ASCII protocol widely used
in the process control industry.
The physical characteristics of the N2 bus is an RS-485 3wire connection, with a maximum of 100 devices
over a 4,000 foot distance, running at 9,600 bps. Logically, the N2 is a master-slave protocol; the supervisory
controller is normally the master. Data is partitioned into common HVAC control objects, such as analog input,
analog output, binary input, and binary output. N2 messaging supports the reading, writing, and overriding of
these points. Additionally, there are messages defined to perform uploads and downloads of devices as well
as to direct memory reads and writes.
The N2 fieldbus protocol supports the following point types:
● Analog Input (AI)
● Analog Output (AO)
● Binary Input (BI)
● Binary Output (BO)
● Internal Integer (ADI)
If Protocol (P5.8.1.1) is set to a value of N2, then configuration and status parameters related to the N2
fieldbus protocol are made available as listed in the Parameters and Monitoring sections below.
Parameters (M5.8.3.1)
The following configuration parameters are available for the N2 fieldbus protocol:
Table 88: N2 Protocol Parameters.
Menu
Parameter
ID
Unit
Mn.
Max.
Default
Description
P5.8.3.1.1
Device Address
2350
1
255
1
Defines the unique slave address to be
used by the drive on the N2 network.
P5.8.3.1.2
Communications Timeout
2351
s
0
255
10
Defines the amount of time in which a
packet is not received before a
communications timeout is
faulted/alarmed.